A wave of attacks on Friday in Kabul killed more than 50 people, primarily civilians and young police cadets, and wounded hundreds.

The bloodshed began when a truck bomb exploded in a heavily populated district of the capital, killing 15. A later suicide bombing at a police academy left at least 25 people dead, the BBC reported. Meanwhile an hours-long battle at a base in Kabul killed 11 people, including a NATO soldier and eight contractors. The UN mission in Afghanistan said the wave of violence was the worst since the organization began recording civilian casualties in 2009.

A Taliban spokesman, Zabiullah Mujahed, said the group was responsible for the attack on the police academy, AFP reports, but no one has yet claimed the other two attacks.

Nicholas Haysom, the head of the UN mission in Afghanistan, agreed. "We suspect the upsurge in violence may be triggered by the succession battle within the Taliban," he told the BBC.

Last week, Afghan authorities announced the death of Taliban leader Mullah Mohammad Omar. According to Afghan intelligence, Mr. Omar died more than two years ago in a hospital in Karachi, Pakistan. The revelation sparked a leadership struggle among senior Taliban figures.

A leadership council last week appointed Mullah Akhtar Mansour, Omar’s deputy since 2010, to head the movement, but he is facing internal resistance, including from members of Omar’s family, The Guardian reports.

Analysts suggest there has been infighting within the group between supporters and opponents of Mansour, which could endanger the peace process that was suspended last week after the announcement of Mullah Omar's death, reports the BBC.

Others suggest the recent violence could be an attempt to display the Taliban's military power ahead of talks.

"We are in a very delicate stage in the peace process. It appears some members (of the Taliban) still want to fight,” Al Jazeera reported after Friday's attacks. "The attacks probably are an attempt by some fighters to show that they still have some power, so that they have some clout when they come to the negotiating table.”

The attacks add to a rising number of civilian casualties in Afghanistan in 2015. In a report published on Wednesday, the UN said more deaths and injuries have been reported this year than any year since the start of the US-led invasion of the country in 2001. Nearly 1,600 civilians have died already this year, said the UN, including a sharp rise in the number of women and children victims.